Before performing data transmission with a base station, user equipment (UE) needs to initiate a random access process.
Generally, in a random access process, UE needs to randomly select an access slot (AS) from a sub-set of access slots defined by a random access channel (RACH) sub-channel that is available to the UE, and send a PRACH preamble to the base station by using the AS. If multiple UEs use a same signature sequence to send, in a same AS, PRACH preambles to the base station, the base station cannot distinguish between the PRACH preambles from the different UEs, causing access failures of the UEs using the same signature sequence. Generally, to improve a coverage capability of a PRACH preamble, UE sends a same PRACH preamble in multiple ASs, so that the base station can perform combined processing on such information that is repeated for multiple times, thereby improving coverage by using a combined gain. However, in the prior art, when UE repeatedly sends a PRACH preamble, a probability increases that multiple UEs use a same signature sequence to send, in a same AS, PRACH preambles to a base station.
Therefore, the prior art has a problem that there is a relatively high probability of an access failure when UE repeatedly sends a PRACH preamble.